The function of a web service in internet applications is to facilitate communication between different software systems over the web. Web services use standard protocols such as HTTP and SOAP to enable interoperability between applications, regardless of their underlying platforms or programming languages. They allow for the exchange of data and services in a scalable and efficient manner. By integrating web services, developers can create more flexible and modular applications, enabling features like APIs (Application Programming Interfaces) for third-party integrations, thereby enhancing functionality and user experience.